Interfacial phonon scattering in semiconductor nanowires by molecular-dynamics simulation

We use molecular-dynamics simulations of vibrational wave packets to study the scattering of longitudinal-acoustic modes from interfaces in semiconductor nanowires of varying diameters. The energy transmission coefficient at the interface is found to depend strongly on both the nanowire diameter and the frequency of the incident wave. By analyzing the scattering events, we determine the selection rules for nanowire scattering that can be understood in terms of the representations of the point-group symmetry of the nanowire. Using such symmetry arguments, we predict that the presence of gaps in the phonon spectrum of thin high-symmetry nanowires will result in a complete reflection of phonons at the interfaces. We discuss the implications of our results for interfacial scattering in real systems, including Si/Ge superlattice nanowires